Tubular heat exchangers are known for a variety of applications. The prior art contains several examples of tubular heat exchangers in which a tube is provided with inner and outer heat exchange surfaces which may be ribbed or corrugated to enhance heat transfer. Such corrugated or ribbed tubes may be formed by extrusion of relatively complex shapes. For example, U.S. Pat. No. 3,887,004 (Beck) describes a concentric tube heat exchanger having an outer tubular shell and an inner splined tube which is preferably formed by extrusion. As shown in FIG. 8 of Beck, a finned structure may preferably be provided inside the splined tube.
It has also been proposed to construct a tubular charge air cooler comprising an extruded aluminum member with two concentric layers spaced by radial splines to provide a flow passage for a first fluid. The second fluid flows through machined grooves formed on the outer surface of the tube.
There exists a need for a simplified, lightweight structure of tubular heat exchangers which avoids use of complex extruded and machined components.